This invention relates to the recovery of oil from subterranean formations by water flood operations, and more particularly relates to the use of sulfonated creosote oil as an additive in surfactant flooding systems.
When water flooding alone is used, oil recovery may be limited due to the relatively poor ability of the flood water to displace the oil remaining in the reservoir's pore structure. Because of the structure of the reservoir and relative surface tensions involved, the flood water may form channels or fingers, bypassing the oil in the formation.
Investigations of ways to increase oil recovery by improving the displacement ability of water floods have produced useful surfactants which reduce the interfacial tension between the oil and water in the reservoir. With lower interfacial tension, oil that is trapped in the pore structure can be dispersed into the water as smaller and more easily deformable droplets. Many types of surfactants have been investigated and the choice of which surfactant to employ in a water flood operation is dependent upon the conditions in the reservoir as well as the cost and availability of the surfactants.
Most water flood operations have employed a petroleum sulfonate as a sole surfactant, or at least a major component of a mixture of surfactants. Synthetic alkyl lauryl sulfonates and alkyl sulfonates and sulfates have all been proposed as oil recovery surfactants. To combat separation problems in surfactant mixtures, a material with both water soluble and oil soluble characteristics is usually added to sulfonate surfactant mixtures. These materials are generally referred to as "solubilizers" and are usually sulfate or sulfonate salts of polyethoxylated alcohols or alkylphenols. The choice and concentration of the solubilizer employed is dependent upon the choice of surfactants used.
U.S. Pat. No. 3,835,183 discloses the sulfonation of an intermediate oil fraction of creosote oil by the use of a spent alkylation acid and subsequent neutralization. Further, Chemical Abstracts 113078m discloses a Russian language publication which describes the sulfonation of tar oil followed by neutralization of the sulfonated product to produce surface-active substances which are at least partially water soluble. See, Mikhailenko, G. I., Klimenko, N. G., Babich, L. E., Basova, L. F., Maslo-Zhir. Prom. 1969, 35(12), 35-6.